GB971503A - Improvements in or relating to electrical measuring instruments - Google Patents

Abstract

971,503. Electric meters. SANGAMO WESTON Ltd. Feb. 1, 1961 [Feb. 1, 1960], No. 3494/60. Heading G1Q. [Also in Division H1] In an electrical measuring instrument, such as a moving coil meter, in which a protective casing surrounds an indication-producing mechanism and at least one resistor or other circuit component is associated with such mechanism, the said component is releasably secured to an internal wall of the casing by means of tongue or groove on the component frictionally engaging a groove or tongue on the wall. As shown, Fig. 1, a meter casing 10 comprises a cylindrical chamber 11 for receiving the meter movement (not shown)and one or more shunt or series resistors, which are mounted in inwardly projecting blocks 27 on the cylindrical wall of the chamber 11. Each block 27 comprises a T-shaped groove 28, tapered at its front end, into which fits a T-shaped tongue 18, Figs. 3, 6, integral with, and extending axially from, a moulded spool 14, e.g. of nylon, on which the resistance wire is wound. The side arms of the tongue have lips 21 and are resilient so that they form a friction-tight fit in the grooves. The spool also comprises an axial blind hole 22 of square cross-section for mounting on a spindle, and two flanges 16, 17, the latter having a small hole 23, which may be formed by the overlap of grooves 26a, 26b on the outer and inner surfaces of flange 17, through which a lead from the inner end of the resistance wire is brought out. The periphery of flange 17 is notched to provide a channel for the lead from the outer end of the resistance wire; when the resistance wire has been wound, baked, impregnated, and value-adjusted, the two leads are laid across a block 25 integral with the external surface of flange 17 and anchored therein by the local application of heat. The tongues and co-operating grooves may be of other cross-section, e.g. dovetail, and the tongue may be on the casing and the groove on the component. Two simple insulating blocks may be mounted in the case by tongue-andgroove means, a wire-ended resistor being mounted thereon by heat-embedding in, or soldering to tags on, the blocks.